A rechargeable battery typically has a useful life between approximately three hundred and one thousand charging cycles. Eventually, due to chemical changes in the electrochemical cells making up the battery, they no longer hold their charge, and require replacement.
Conventionally, when a rechargeable battery reaches the end of its life, the user purchases a new one, or sends the spent battery to a rebuilder, who will install new cells and spot-weld connectors to them using industry-specific welding equipment. Both conventional solutions are costly, and the latter solution, professional rebuilding, is also time-consuming, and puts the cordless tool out of service for the time required for rebuilding, unless the user maintains a spare battery.
There are numerous different kinds of rechargeable batteries for cordless tools, and these batteries having varying numbers of cells and a variety of different cell arrangements. Because of the variety of batteries, it is impractical for anyone to supply replacement kits consisting of replacement cells with their electrical interconnections already made.
A user can obtain individual replacement cells, but the expensive specialized welding equipment needed for battery rebuilding is beyond the means of most ordinary users. On the other hand, an attempt to solder connections to the replacement cells, will often overheat the replacement cells and ruin them. In the case of attempts to solder connections to lithium ion (Li ion) cells, there is a significant risk of explosion and personal injury.